Electrical Hot alternator while ignition is in the on position

S

Swhitney

Active Member

Feb 11, 2019

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Oregon City

Jul 9, 2021

#1

• Jul 9, 2021

• #1

I had to move the car in my garage, so I turned the ignition on (engine off) to push the car around. I forgot about the key being in the on position until I came back a few hours later to smell something a bit strange. What I found is the alternator was hotter than hot, and now it seems like the bearing is toast in new 130 amp alternator.

What would cause the alternator to heat up?

1992 Mustang GT
302 engine
130 amp alternator (Amazon)

 

90sickfox

Wasn't a pretty sight...and I've got big hands

SN Certified Technician

Mar 2, 2015

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Jul 9, 2021

#2

• Jul 9, 2021

• #2

That alternator has an internal short. Good thing you weren't driving it when it happened. If the battery connection at the alternator is loose it'll cause the stud to get hot. Usually, the alternator would have to be running for that.

 

Reactions: jrichker and 2Blue2

S

Swhitney

Active Member

Feb 11, 2019

184

10

28

Oregon City

Jul 9, 2021

#3

• Jul 9, 2021

• #3

90sickfox said:

That alternator has an internal short. Good thing you weren't driving it when it happened. If the battery connection at the alternator is loose it'll cause the stud to get hot. Usually, the alternator would have to be running for that.

Click to expand...

So you think it's not something else? Brand new alternator has a short, seems strange right?

 

90sickfox

Wasn't a pretty sight...and I've got big hands

SN Certified Technician

Mar 2, 2015

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Jul 9, 2021

#4

• Jul 9, 2021

• #4

Not strange at all. Quality control is way down. Something shorted inside that thing....or got so hot that it melted and shorted out. Dodge had a problem with this recently. Their cars would catch fire because of it.

 

JD1964

there is enough sticking out to grab on to

15 Year Member

Jun 28, 2013

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Jul 9, 2021

#5

• Jul 9, 2021

• #5

I had a relatively fresh 130 amp alternator cook the + post and connector on the back of the alternator. Im not totally sure what caused it but the alternator was not a cheap one. I had gotten it from one of the Mustang specific vendors. I replaced it with a DB Electrical unit which I got from Amazon. I've had no trouble with the new one, albeit I also upgraded the wiring.

Here's the one I have now. It may need to be clocked to use on the Foxbody application. It's still a decent price I think.

Amazon product ASIN B007XUIF52View: https://www.amazon.com/gp/product/B007XUIF52/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

 

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Blown88GT

Founding Member

Nov 13, 1999

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Palm Beach Gardens, FL

Jul 12, 2021

#6

• Jul 12, 2021

• #6

Swhitney said:

I had to move the car in my garage, so I turned the ignition on (engine off) to push the car around. I forgot about the key being in the on position until I came back a few hours later to smell something a bit strange. What I found is the alternator was hotter than hot, and now it seems like the bearing is toast in new 130 amp alternator.

What would cause the alternator to heat up?

1992 Mustang GT
302 engine
130 amp alternator (Amazon)

Click to expand...

The alternator field is energized when the ignition is on. Turn ignition on & any steel item will stick to alternator case.